Electric indicator for grinding machines



Sept. 16, 1941. H; J. LOVENSTON ELECTRIC INDICATOR FOR GRINDING MACHINES Filed ma 20, 1940 2 Sheets-Sheet 1 INVENTOR.

HANS J. LOVENSTON BY ATTORNEYS Sept. 16, 1941. H. J. LOVENSTON 2,256,120

ELECTRIC INDICATOR FOR GRINDING MACHINES Filed May 20, 1940 2 Sheets-Sheet 2 INVENTOR.

HAN s J. LOV EN STON A TTORN E YS Patented Sept. 16, 1941 UNITED STATES PATENT OFFICE ELECTRIC INDICATOR FOR GRINDING 1 Y MACHINES Hans J. Lovenston, Detroit, Mich, assignof to Gear Grinding Machine Company, Hamtramck, Mieh a corporation of Michigan Application May 20,1940, Serial No. 336,315 4Claims. (01. 177-411) Itis the object of the invention to obtain indi-; cating means'for grinding machines which will enable the operator to-determine whether the grinder is" in contact with the work, this being particularly useful where such contact is con cealed from direct observation. To this end the invention consistsrjfirst in an electrical signal circuit operated by contact of a portion'of the grindingsurface with the--work; and second in,

the peculiar construction";ofthe grinder wheel whicha'dapts-it for this-purpose. 1

In the drawings;

Figure 1 is asectional elevation'showing one form of myimproved indicating mechanism;

Figure 2 is a'similar view illustrating a modifled construction} I Figure 3 is a similar view showing another modification; Figure 4 is a side eleva'tionof Figure 3; Y Figure 5'is a diagrammatic view showing'another modification.

In the grinding of 'certainclasses oi work'the grinder'wheel may be completely concealed from view, 'so that'the operator cannot know by obf serva'tion whether or not the grinding ;'surface is method is to incorporate'a certain amount of,

electrically "conductive material with the dielecme abrasive material during the manufacture of the grinder wheel, so thatthe latter will be rendered sufficiently conductivelfor the purpose. Still another methodis to render the grinder wheel conductive as just described, but to insulate-one portion thereof 'from anotherportion' so that separate signals may be used to indicate. which por-,

tion is in contact with the work. a y

More in detail and as shown diagrammatically in Figure 5,A'is an ordinary grinder wheel which is formed of dielectric al abrasive material, and B y is the arbor on which this wheel ismounted by.

in contact withthe surface to be; ground. With other grinding operationssuchffor instance, as in the form grinding of' gear teeththe opposite sides of thejgririding wheel'ifashion adjacent tecthfand itma'ybe difficult for'the operatortohetermine which side isjinflcontactor whether both are -si multarieouslyj in Contact. [I have, therefore, dd- J vised a construction of signal mechanism in which'an electrical 'ci rcuit is closed by contact. of the grinding surface or a portion thereof with thesur'f ace to be ground so as tooperate Ialv'i'sual,

or audible signaL 'Thereis however, one difiiculty the wayjof accomplishing this purpose due to the fact th'atfmany grinder wheels are formed. of; abrasive material of a' dielectric'al character. Wheze such' wheels are used for grinding metal or other electrically conductive material the portion of the surface in contact with the work may become loaded with the grindings so as to be rendered conductive. but the difficulty remains of completing the electrical conncction between this portion of the surface and the external circuit. One method of accomplishing the purpose is to use grinder wheels of a dielectrical character and to provide an electrically conductive surface coating extending from the portion actually contact with the work' to a point radially inward therefrom Where it may be connected with an external conductor. Such construction is illustrated in Figure 5. Another means of a' clamping nut B. C is a facing of conductive material extending radially onone or both sides of'the wheel and contacting with-a conductive ring C' mounted on an. insulator" sleeve C on the spindle v A brush D bearing against the ring C will serve to conduct the current to an external circuit D including a'signal light D? an'dthe portion .133 grounded on the frame of a the machine. .With this construction after the peripheral surface of the grinder wheel becomes loaded with, metal a circuit will be formed whenever this surface, contacts with the 1 work E and will be 'broken by separationv of the grinder from the work! 4 l ith the construction shown inll igurelthe; grinderwheel li is electrically conductive, but is separated from the arbor G by an insulator sleeve. or bu shing, GT and insulator disks G? and G at; opposite e ends the reof; His an ele'ctrically conductive tube having an inwardly extending shoul-j, der Hf engaging the disk G2, 801M131} when the wheel is clamped by the nut G =it will-be. thoroughly insulated from the arbor by an elec I trical connection with the sleeve-H. iAbr-ush H contacting with this sleeve will carry the current to ,the external circuit (notshown). ;-Such. con struction permits of grin-ding inside of a tubular member, such as indicated at I, and which would conceal the grinder wheel during the performance of its work. The signal will indicate whenever the grinder wheel makes or loses contact with the work. i

In the construction shown in Figure 2 the grinder wheel J formed of conductive material is clamped on its arbor J in the ordinary way and without being insulated therefrom. The arbor is revolved by pulleys J 5 which may be driven through belts of dielectrical material, so that the whole structure is insulated. The external circuit (not shown) is connected to the grinder wheel through a conductor J so that acircuit partition K ed into the wheel duringthe formation thereof,

and maybe made of suitable dielectrical ma out the entire v I This is preferably accomplished by placing; the

will be established through the grinder wheel wheneverit contacts with the work. 7 1 The construction shown in Figure 3 is designed for the form grinding of gear wheel teeth. The

grinder wheel K has its peripheral portion fashioned for insertion between adjacent teeth of the gear wheel to grind the faces thereof to cor-j rect form. It is essential that both gear teeth should be ground to correctly form the contours thereof, .an'dtherefore. the operator should be similar construction isused for the circuit l' onf nected to the conductor P.

to the portions K and K In the operation 'of the construction last de-- scribed, the signal circuits connected respectively of the grinder wheel are separate and distinct from each other so that if only one of thesecircuits is energized the operator will at once he made aware of the fact that both of the fashioned sides of the grinder a's'indicatin'g-the particutlarside 'which.is. This warnedifeither side of the grinder wheel failst'oi contact with its respective tooth. To accomplish this result the grinder wheel is formed in two electrically conductive portions 'Kf and K which are separated from each other by a 'dielectrical This partition is preferably moldterial, such as melted sulphur, which will have the'requisite mechanical strength and will firmly The formed por-' bond to the abrasive material.

tions of the wheel K and K are trimmed to the exact cross sectional contour desired, but the V peripheral portion K ralso functions to grind the bottoms'of the interdental spaces.' Conse quently', if the partition K were arranged parallelitothe?! plane of rotation there would be a;

portion 'of' the peripheral surface Ki lwithout abrasive material so that it would fail to properly function. This diiiiculty I have avoided by ar ranging the peripheral portions of the partition K which 'are'on opposite sides of the axis of,

the wheel/slightly ofiset from, each other so as c to obtain "a: trace of abrasive material through width of the peripheral portion K partition K ina' plane slightly inclinedfto the c axis and fashioning the abrasive portions of the; wheel which" are on opposite sides thereof to. 7 ccmpensatefor this inclination; The wheel K is mounted on an insulator sleeve L surrounding the arbor L" with COIidUCtOt'diSks M and M contacting the-portions K and K. L and :L separate the disks M tively from'the shoulder'L onthe arbor and the clamping nut L 1 A wheel" guard N covers the upper i'portionflof the wheel .K and brushes 0' and. O- secured on insulator blocks 0? and O mounted on the guard respectively contact with the; peripheries or the'gdisksiMand M. Insulated conductors Pand P' leadfrom the respec- 1 'tive brushes :to separate external circuits, such for'instanc'e as diagrammatically represented at- 1 the right, Figure 3, including a. service conductor Q, resistors Q and Q respectively connecting said service with the conductor P and a ground Q A tube Q is-connected in shunt with the resistance Q and operates a suitable relay Q controlling a switchQ in a circuit Q including the signal light. Q arrangement'is such that whenever the circuit is closed by contact of theflportionj K? of the' grinder wheel with the work, the signal light Q will-be displaced. A

Insulator disks f and, M respecv wheel are not in contact with; the work; as well insures that before the work is finished proper adjustments will be made to correctly formall of theworking surfaces of allrof the teeth.

. What I claim as my invention is;

1. An electrically conductive grinder whe electrical signal circuit connected with each porwith the work will 2. A rdisk-shap ed grinder and an intermediate dielectrical portion, an insulator mounting for saidowheel on its-driving spindle, and a separate external electrical signal circuitconnected with each portion of said wheel and'including'the work tobe ground "whereby:v the contact of the grinding said portions will be indicated by its correspond-r fing signal circuit. a V I g r ,3. A disk-shaped grinder wheel havingopposite electrically electrical portion extending to'the' periphery of Y the disk but'being ofiset in difierent portionslof said periphery to form abrasive grinding. portions the full width thereof, an insulator mounting for said wheel, and a separate external signal circuit a portion of said wheel and a 7 including the work to 'be ground whereby the' contact of thegrinding surface of each of said connected with each portions with the work will be'indicated by its corresponding signal circuit.

1 4. A disk-shaped grinder wheel having oppc- V site-electrically'conductive abrasive side portions andan intermediate dielectrical portionthe lattext-extending tothe periphery of .the wheel and being arranged in a plane slightly oblique to the plane of rotation of the wheel sides thereof, and'to' form grinding portions the full width of the'periphery of said wheel, an insulator mo'untingfo'r said wheel and a separate external'signal circuit connected with eachportion of said wheel and including the work to be ground, whereby the contact of the grinding surface of each of said portions with the work will be indicated by its corresponding signal circuit. HANS J. LOVENSTON.

surface of either of V V conductive abrasive side portions and an intermediate diele'ctricalportion, saiddiso as to offset the peripheral portions on diametrically opposite 

